System made up from three main parts: vacuum switch, combination transformer, control box. Combined transformer has two types: three-phase three-wire,three-phase four-wire, also according to user requirements, add two more winding for over current protection, zero-sequence protection.

With over current protection controller in the control box, measuring the sub-selection smart prepaid energy meter can be realized prepayment features, select wireless remote monitoring terminal, either by remotely read meters data and instructions terminal complete the prepay and load control programs, achieve the purpose of remote monitoring. Classification and function by prepayment metering box with different structure divided into three types:

2 Switch for the vacuum circuit breaker with integrated structure.

Combined transformer ZW8 or ZW32 assembled a body of vacuum circuit breaker, combined transformer with overload protection and zero-sequence protection of winding, to change the traditional switch structure, optimize the over current protection function. Features: suitable for large currents, high breaking capacity, integrated design is easy to install.

3 Switch for vacuum circuit breakers split type.

Zw8 or combination of ZW32 vacuum circuit breaker and transformer is an independent structure, assembled together to achieve prepayment features when installing. To select the combined transformer with overload protection and zero-sequence protection of winding, to change the traditional switch structure, optimize the over current protection function. Features: suitable for large currents, high breaking capacity, installation flexibility, split body structure, easy to replace damaged parts, reducing maintenance costs.